Mercury switch



July 24, 1934. c. H. LARsoN MERCURY SWITCH Filed Jan. 3, 1955 Ca/ HL M5072/ Patented-July 24, y1934 UNITED STATES MERCURY SWITCH Carl H. Larson, Elkhart, Ind., assignor to The.

Adlake Company, a corporation of Illinois Application January s, leas, serial No. 649mmL It is often desirable to use mercury switches in A electrical circuits that require a given time iiiterval between the functioning of the switch actuating mechanism and the making and breaking 16 Claims.

l of the circuit controlled by the switch.

, The presentinvention provides a simple means for accomplishing this result, and switches made in accordance withI this invention are particularly useful because of their wide` range of adjustment and the many functions which they canbe made to perform. l

Other objects of the invention are to provide a switchthat is economical in manufacture, reliable in service, andwhich possesses a long useful life;,to protect the vulnerable parts of the switch from the deteriorating effects of the arc;

and to provide external means for adjusting the time delay of the switch.

Further and other objects and advantages of the present invention will become apparent as I, the disclosure proceeds and the description is read in conjunction with the accompanying drawing, in which thimble;

Fig. 4 shows what happens immediately subsequent tothe' de-energization of the coil;

Fig. 5 is a modification 4of the switch showny in Figs. 1-4 inclusive. In this case, the displacer normally closes the electrical circuit across the electrodes when the associated coil is de-energized. l

Fig. 6 shows the switch, in open circuit position.

l Fig. 'leillustrates a modification designec to effect a quick breaking and slow making of the electrical circuit; and

Fig. 8 is a vertical, sectional view of a modified illustrated in Fig. 5,

form of plunger which may be used with or without the inverted thimble.

l But thisjspeciflc illustration and the correspondingly specific description are for the purv pose of disclosure only and are not to be construed as imposing limitations upon the appended claims except'as may be required by the prior art.

' Referring rst to Fig. 1, a switch 10 is Shown (ci. zoo-97) mounted within a coil 11 havinga winding 12 suitably connected to a control circuit.` As the circuit is of no consequence to the present invention, it is not shown.

The coil 11 includes a spool 13 having a central opening 14 adapted to receive circular pole sleeves 15 and 16. The pole sleeves are heldin place by clips 17 fastened to the end of an iron yoke 18. The yoke serves as an exterior path for the magnetic flux. f

The pole sleeves 15 and 16 are made of magnetic material and with the iron yoke 18 form a magnetic circuit which is closed except for the j air gap 19 between the adjacent ends of the pole sleeves.4 The yoke 18 is preferably laminated for use with alternating current.

-The switch 10 comprises a glass envelope 20 A through the bottom of which electrodes 21 and 22 are sealed. The electrode 21 is provided with an insulating sleeve 23 to a point 24 leaving the upper portion of the electrode bare. The electrode 22 is uninsulated.

A charge of mercury 25 within the envelope is adapted tomake or break ran electrical circuit through the electrodes 21 and 22, according to its level.

-A displacer, or plunger 26, made`of iron, or iron and some other material, floats on the mercury and is adapted to be drawn downwardly when the coil 11 is energized to raise themercury level and bridge the electrodes 21 and 22 with mercury. The displacer is provided with lugs 27 to guide the vertical movement of the plunger within lthe switch envelope.

An inverted thimble 28 .of porous material is telescoped over the central electrode 21 and is secured in place by any suitable means. In the present case, the thimble is secured to 'the top of the electrode 21 by an oxyphosphate zinc cement, indicated at 29. It will be understood that the thirnble could be secured to any otherfxed'part of the switch. After the switch parts have been assembled within the envelope 20 and the necessary adjustments have been made, the envelope is evacuated and lled Ywith a suitable inert gas, such as helium, hydrogen, nitrogen, etc.

The porous material used for the thimble 28 is preferably a ceramic and a product known as Alundum manufactured by the Norton Com pany, Worcester, Massachusetts has been found very satisfactory. One of three principal grades RFA-84 dense, R-A-360 medium, and R-A-98 coarse, may be selected, according to the specications of the switch.

Springs 30 and 31 are provided to cushion the ends of the switch against sharp impact with the plunger.

The operation of the switch is as follows: When the coil 11 is de-energizedfthe plunger 26 heats upon the mercury as shown in Fig. 1 and the electrodes 21 and 22 are insulated from each other. When the coil 11 is energized, the plunger 28 is quickly lowered to close the air gap 19. The lowering of the 'plunger immediately displaces the mercury on the inside and outside of the plunger, but mercury is temporarily restrained from rising within the thimble 28 because of the gas trap formed within the thimble. This is clearly shown in Fig. 2. 1

Due to the inequality of the gas pressures within and outside the thimble 28, gas slowly escapes through the porous material to the outside, and the mercury column in the thimble slowly rises. After a given time interval, which is dependent upon such factors as the porosity of the thimble 28, the height of the outside mercury level and the particular gas that is used for a fill, the mercury nally rises above the top of the insulation 23 surrounding the electrode 21 and establishes an electrical connection between the electrodes -porous material into the interior of the thimble,

the mercury slowly recedes until it passes the point 24 at which time the circuit is broken through the electrodes 21 and 22.

, It is obvious that the time delay for making or breaking a circuit through the electrodes 21 and 22 may be varied in several ways. For example,

the height of the insulating sleeve 23 determines in part the relative time delay between the making and breaking of the circuit. 'I'he porosity of the material which comprises the thimble 28 de- I termines the rate at which the gas escapes or enters the thimble and consequently is a factor in determining the time delay. The depth to which the plunger or displacer is drawn dete'rmines the height of the mercury column on the outside of the thimble and hence is partly deter- I. minative of the diierence in pressure between the inside and outside of` the thimble. Thenkind of gas used for the gas ll is also a factor.

In testing the switch during the process ofi manufacture, accurate time delays may be made by applying dabs of cement to the surface of the thimble 28/to vary its effective surface.

The travel of the plunger 26 may be controlled by'moving the entire switch 10 relative tothe coil 11, or at least relative to the air gap 19. This isaccomplished in the present instance by providing acap 32 cemented or otherwise secured to the top of the envelope and having an upwardly extending threaded stem 33 adapted to pass through a suitable aperture 34 in a bracket or other fixed support. A knurled nut 35 threaded on the stem which differs from the form of the invention shown inFigs. 1 4 inclusive by having the plunger 'or rechace sition will rest upon the spring 31. Consequentlythe `electrode 21 is shorter in length. As long as there is no magnetic ilux across the air gap 19, the plunger remains in the position shown in Fig. 5 with mercury bridging the electrodes 21 and 22. When the coil 11 is energized, the plunger is immediately lifted, as shown in Fig. 6, and the mercury level on the outside of the thimble' immediately drops below the top of the insulating sleeve which surrounds the central electrode 21. Recession of the mercury within the thimble 28,l however, is delayed in exactly the same manner as previously described, with reference to Fig. 4.

Similarly, when the plunger 38 is dropped from its raised position by de-energization o f the coil l1, the same action of the switch elements takes place, as shown in Figs. 2 and 3.

In Fig. 7, another modification of the invenw tion is shown which is designed to make. the time delay element inoperative when the` circuit is being broken. This is accomplished by providing a thimble 39 similar in all respects to the thimble 28, except that the bottom of the thimble is positioned slightly above the top of the mercury level when the switch is in open circuit position. 'I'hus when the plunger is pulled down (as in Figs. 1-4) or allowed to drop (Figs. 5-6) the mercury level is delayed as before in its upward movement within the thimble, thereby providing the required time delay for making the circuit through the electrodes 21 and 22. When the. plunger is raised, however, either by magnetic force (Figs. 1-4) or by buoyancy (Figs. 5 6) the mercury level immediately drops below the` bottom of the thimble 39, and undermines the mercury column within the thimble, thereby causing it to immediately and quickly fall from the thimble.. In this manner, the electrical circuit controlled by the electrodes 21 and 22 is slowly made and quickly broken.

The plunger 26 of Figs. 1, 2, 3, 4, and '7, and the plunger 38 of Figs. 5 and 6, or any other suitable plunger may be equipped with a porous head 40, as shown in 8. It may be made of the same material of which the inverted thimble is vslowly admitted into the plunger through the porous wall 40. If magnetic force is used to raise the plunger, the air gap may be so 'positioned that the plunger is completely lifted out of the mercury, in which case the mercury column within the plunger is undermined, and the electrical connection between the electrodes 21 and 22 quickly broken. In this respect, the action is similar to that of the switch shown in Fig. 7.

If the plunger shown in Fig. 8 is used in combination with the thimble 28, the action of the switch will correspond to the action of the switches shown in Figs. 1-7, except that greater time delays are possible in this way.

, It will be noticed that the switch structures shown in Figs. 1-7 inclusive, in addition to possessvelopes are protected from the deteriorating efi'ects of any arcing that may occur at the central electrodes. 'Ihis is particularly important where the switch is subjected to heavy loads.

Other modiflcationsof the invention will be apparent to those skilled in-the art. For example, the thimbles 28 and 39 may be made of non-porous material and provided-with a small opening adjacent the top for permitting a restricted flow of gas from the interior to the outside of the thimble, and vice versa.

What I claimktherefore, is:

1. In a mercury switch, a sealed vertical envelope, spaced electrodes in the envelope, a' gas iill, a charge of mercury adapted to close or open a circuit acrossI the electrodes, according to its level, a displacer movable vlwithin the envelope to displace the mercury, and means for retarding movement of a portion of the mercury to eiect a given time delay, said means including an inverted thimble of porous material held in fixedposition over one of the electrodes.

2. In a time delay niercury switch, a sealed vertical envelope, spaced electrodes in the envelope, a gas iill, a charge of mercury adapted to close or open the circuit across the electrodes, according to its level, a displacer movable within the envelope to displace the mercury, and an inverted thimble of porous material held in xed position over one of the electrodes, said thimble delaying movement of mercury to circuit closing position when the displacer is lowered.

3. In a ,time delay mercury switch,a sealed vertical envelope, spaced electrodes in the envelope, a gas fill, a charge of mercury adapted to close or open the circuit across the electrodes,

according to its level, a displacer movablewithin the' envelope to displace the mercury, and an inverted thimble of porous material held in xed A positionover one of the electrodes, said thimble delaying movement of mercury to circuit closing position when the displacer is lowered, and the movement of mercury to circuit opening position when the displacer is raised.

' 4. In a time delay mercury switch, a sealed vertical envelope, spaced electrodes in the envelope,

a gas iill, a charge of mercury adapted to close or open the circuit across the electrodes, according to its level, a displacer movable within the envelope to displace the mercury, and an inverted thimble of porous material held in xed position over one of the electrodes, the bottom of the thimble being slightly above the levelof the mercury when the switch is in open circuit position so as to eiect a slow making and fast breaking of .the circuit. Y

5. In a time delay circuit breaker, a lmercury 4switch comprising a sealed vertical envelope,

spaced electrodes in'the envelope, a charge of mercury adapted 'to close or open the circuit across the electrodes according to its position, a time delay element in the switch, and means external of the switch for varying -the action of said element.

- 6. In a time delay circuit breaker, a mercury switch having a' sealed vertical envelope, spaced electrodes in the envelope, a charge 'of mercury adapted to close or open the circuit across the electrodes, according to its level, a displacer movable within the envelope to displace the mercury., a time delay element in the switch, and means externalof the switch for varying the action of said element.

'7. yIn a time delay circuit breaker, a mercury switch comprising Aa sealed vertical envelope,

spaced electrodes in the envelope, a charge of mercury adapted to close or open a circuit across the electrodes, according to its level, a displacer within the envelope for displacing the mercury, a coil for magnetically controlling the movement of the displacer, a time delay element in the switch and means for moving the switch relative to the coil to vary the action of the time delay l mercury, a coil for magnetically controllingthe Y movement of the displacer, a time delay element in the switchand means for moving the switch relative to the coil to vary the action of the time delay element, said means including a slow motion adjustment.A

9. In a mercury switch, a sealed vertical envelope, spaced velectrodes in the envelope, a gas lill, a charge of mercury adapted to close or M open a circuit across the electrodes, according to its level, a displacer movable within the envelope to displace the mercury, and means for retarding movement of a portion of the mercury to effect a given time delay, said means including van inverted thimbletelescoped over one of the electrodes and provided with a gas relief vent, said thimble being fixed with respect to said electrode. n 10. In a mercury switch, -a sealed vertical envelope, spaced electrodes in the envelope, a gas ll, a charge of mercury adapted to close or open a circuit across the electrodes, according to its level, a displacer movable within the envelope to displace the mercury, and means for retarding movement of a portion of the mercury to effect a given time delay, said means including an inverted cup-shaped element held in fixed position over` one of lthe electrodes and equipped with a restricted gas passage.

11. In a time delay mercury switch,- a sealed vertical envelope, spaced electrodes in the envelope, a gas fill, a charge of mercury adapted to close or open the circuit across the electrodes, according to its level, a displacer movable within the envelope to displace the mercury, and an inverted cup-shaped element heldin fixed position over one of the electrodes, said element having a restricted gas passage whereby the movement of gmercury to circuit closing position is delayed when the displacer is lowered.

12. In a time delay mercury switch, a sealed vertical envelope yspaced electrodes in the envelope, a gas ll, a charge of mercury adapted to Iclose or open the circuit across the electrodes, ac-

the envelope to displace the mercury, and an inverted cup-shaped kelement held in xed position over one of the electrodes, said elementy having a restricted gas passage and being positioned with its bottom slightly above the level of the mercury when the switch is in open circuit position so as to effect a' slow making and fast breaking ot the circuit. 1

13. In a mercury switch relay adapted to introduce atime delay between the functioning of a control circuit and a main circuit, the combina'- tion'of` a coil, a switch envelope associated with thel coil,'a mercury fill, and means responsive to the coil for retarding movement of a portion of the mercury to effect a given time delay after the condition of the control circuit has been changed,

mercury level, said displacer being closed at its top except for a restricted gas passage, and an inverted cup-shaped element held in xed position over the same electrode, said element also being provided with a restricted gas passage.

15. In a time delay circuit breaker, a mercury 'switch comprising a sealed'vertical envelope,

spaced electrodes in the envelope, a charge of mercury adapted to close or open a circuit across menage the electrodes, according vto its level, a displacer movable within the envelope for displacing the mercury, a coil for magnetically controlling the movement of the displacer, a time delay element in the switch, said switch being movable relative to the coil for varying the action of the time delay element. Y Y

16. In a time delay circuit breaker, a-mercury switch comprising a sealed vertical envelope, spaced electrodes in the envelope, a charge of mercury adapted to close or open a circuit across they electrodes, according to its level, a displacer movable within the envelope for displacing the mercury, a coil for magnetically controlling the movement of the displacer, a time delay element in the switch, and means for changing the relation of the magnetic eld to the switch for varying the action of the time delay element.

. CARL H, LARSON. 

